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BQ25720: The BQ25720EVM board does not charge the battery without system load (when VSYSMIN was set higher than VBAT. )

Sven Zhao
Prodigy 30 points
Part Number: BQ25720

Dear sir,

I am using the BQ25720EVM board to some test and found if there is no system load connected, only connect battery, the charger will not charge the battery even after correctly setting the charge current and voltage. 

The charger action will start if I connect a system load to the board.

here is the log from BQ studio 

Fullscreen 202405171530.log Download 
Fri May 17 15:31:02 CST 2024

Device Name = BQ25720
Firmware Version = 1.00


Sample,DateTime,ElapsedTime,Charge_Option_0,Charge_Current,Max_Charge_Voltage,OTG_Voltage,OTG_Current,Input_Voltage,Min_System_Voltage,IIN_HOST,Charger_Status,Prochot_Status,IIN_DPM,ADC_VBUS_and_PSYS,ADC_IBAT,ADC_IIN_and_CMPIN,ADC_VSYS_and_VBAT,Manufacture_ID,Device_ID,Charge_Option_1,Charge_Option_2,Charge_Option_3,Prochot_Option_0,Prochot_Option_1,ADC_Option,Charge_Option_4,Vmin_Active_Protection,TM1_0,TM3_2,TM5_4,TM7_6,TM9_8,TM11_10,TM13-12,SFT1_0,SFT3_2,SFT5_4,SFT7_6,SFT9_8,SFT11_10,SFT13_12,SFT15_14,SFT17_16,SFT19_18,SFT21_20,SFT23_22,SFT25_24,SFT26,LOUT,LogRowTime(ms),LogStatus
1,2024-05-17 15:31:06,4.003,,0000,4010,09C4,3C00,3200,AF00,4100,8000,B800,4100,C000,0000,00FF,E9B3,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,960,ERROR : Please check D:\auralis\BATTERY CHARGER BQ25720EVM\202405171530.log.err
2,2024-05-17 15:31:10,8.010,E70E,0000,4010,09C4,3C00,3200,AF00,4100,8000,B800,4100,C000,0000,00FF,E9B2,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,733,SUCCESS
3,2024-05-17 15:31:14,12.012,E70E,0000,4010,09C4,3C00,3200,AF00,4100,8000,B800,4100,C000,0000,00FF,E9B3,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,1138,SUCCESS
4,2024-05-17 15:31:18,16.024,E70E,0000,4010,09C4,3C00,3200,AF00,4100,8000,B800,4100,C000,0000,00FF,E9B2,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,736,SUCCESS
5,2024-05-17 15:31:22,20.032,E70E,0000,4010,09C4,3C00,3200,AF00,4100,8000,B800,4100,C000,0000,00FF,E9B3,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,744,SUCCESS
6,2024-05-17 15:31:26,24.046,E70E,0000,4010,09C4,3C00,3200,AF00,4100,8000,B800,4100,C000,0000,00FF,E9B3,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,1120,SUCCESS
7,2024-05-17 15:31:30,28.057,E70E,0300,4010,09C4,3C00,3200,AF00,4100,8000,B800,4100,C000,0000,00FF,E9B3,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,733,SUCCESS
8,2024-05-17 15:31:34,32.058,E70E,0300,4010,09C4,3C00,3200,AF00,4100,8000,B800,4100,BB00,0000,00FF,DEDF,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,732,SUCCESS
9,2024-05-17 15:31:38,36.063,E70E,0300,4010,09C4,3C00,3200,AF00,4100,8000,B800,4100,BD00,0000,00FF,DFDF,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,729,SUCCESS
10,2024-05-17 15:31:42,40.063,E70E,0300,4010,09C4,3C00,3200,AF00,4100,8000,B800,4100,BC00,0000,00FF,DFE1,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,729,SUCCESS
11,2024-05-17 15:31:46,44.074,E70E,0300,4010,09C4,3C00,3200,AF00,4100,8000,B800,4100,BF00,0000,00FF,E2E4,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,733,SUCCESS
12,2024-05-17 15:31:50,48.088,E70E,0300,4010,09C4,3C00,3200,AF00,4100,8000,B800,4100,BF00,0000,00FF,E0DE,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,734,SUCCESS
13,2024-05-17 15:31:54,52.101,E70E,0300,4010,09C4,3C00,3200,AF00,4100,8000,B800,4100,B100,0000,00FF,E2E3,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,738,SUCCESS
14,2024-05-17 15:31:58,56.101,E70E,0300,4010,09C4,3C00,3200,AF00,4100,8000,B800,4100,B100,0000,00FF,E2E4,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,753,SUCCESS
15,2024-05-17 15:32:02,60.105,E70E,0300,4010,09C4,3C00,3200,AF00,4100,8000,B800,4100,C000,0000,00FF,DFDD,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,796,SUCCESS
16,2024-05-17 15:32:06,64.105,E70E,0300,4010,09C4,3C00,3200,AF00,4100,8000,B800,4100,BF00,0000,00FF,E1E2,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,842,SUCCESS
17,2024-05-17 15:32:10,68.117,E70E,0300,4010,09C4,3C00,3200,AF00,4100,8400,B800,4100,B000,0000,00FF,E1E0,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,893,SUCCESS
18,2024-05-17 15:32:14,72.125,E70E,0300,4010,09C4,3C00,3200,AF00,4100,8400,B800,4100,B000,0000,00FF,E0DF,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,1338,SUCCESS
19,2024-05-17 15:32:18,76.138,E70E,0300,4010,09C4,3C00,3200,AF00,4100,8000,B800,4100,C000,0000,00FF,E0DE,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,934,SUCCESS
20,2024-05-17 15:32:22,80.151,E70E,0300,4010,09C4,3C00,3200,AF00,4100,8000,B800,4100,B100,0000,00FF,E1E1,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,953,SUCCESS
21,2024-05-17 15:32:26,84.162,E70E,0300,4010,09C4,3C00,3200,AF00,4100,8000,B800,4100,C000,0000,00FF,E0DF,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,990,SUCCESS
22,2024-05-17 15:32:30,88.174,E70E,0300,4010,09C4,3C00,3200,AF00,4100,8000,B800,4100,B200,0000,00FF,E2E2,0040,00E1,3300,00B7,0434,4A81,41A0,A0FF,0048,006C,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,FFFF,1009,SUCCESS
.

Appreciate if you could help to check it an expected behavior of the chip as I did not find the detail in datasheet about the system load must connected? and what if I only would like to use the charger board to be a battery charger without system load? 

Thanks 

Best regards

Sven Zhao

  • 0
    Prodigy 30 points

    Another imformation is before the charging, we have set the minimum system voltage to 18V which is higher than battery voltage 16.8V.

  • 0 in reply to Sven Zhao
    TI__Mastermind 33275 points

    Hi, Sven,

    We usually set min system voltage lower than the battery voltage. Otherwise, if BATFET is turned on, the battery runs into over-voltage protection. 

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    Prodigy 30 points

    Thanks Tiger,

    But I saw there is LDO mode for the charger which allows the charger system voltage higher than battery charger voltage and the BATFET is suposed to be partially turned on the achieve loewr voltage to charge the battery, could we use this feature to the fit my system that the min_system_voltage is always higer than the battery voltage ?

    Best regards

    Sven Zhao

  • 0 in reply to Sven Zhao
    TI__Mastermind 33275 points

    Hi Sven,

    It is not suggested to charge in LDO mode, the loss is high, efficiency is low. However, after battery is fully charged, you can then raise the min system voltage higher than the battery voltage and disable charge at the same time.

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    Prodigy 30 points

    Thanks Tiger,

    Another thing that I found the system voltage will be pulled as high as charger voltage when I set the min_system_voltage lower than battery voltage during charging, but our system prefer constant system voltage, this is the reason that I set the min_system_voltage at a higher level than the fully charged battery voltage to ensure the system voltage is at a stable value. could you suggest is there a way to keep the system voltage at a stable level not matter the chip is charging or not charging? or this chip is not designed to do that?  many thanks.

    Best regards

    Sven Zhao 

  • 0 in reply to Sven Zhao
    TI__Mastermind 33275 points

    Hi, Sven,

    The system operates like that. I don't see any issue here. 

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    Prodigy 30 points

    Thanks Tiger,

    I mean, if my system want a stable system voltage all the time no matter charging or not, I may need another circuit to stablize the output system voltage from BQ25720 right? 

    Because I measured that the system voltage from BQ25720 may change among min_system_voltage, battery voltage and max_charge_voltage depends on different conditions ( battery connected or not, charging or not), just checking my understanding is correct?

    Thanks.

    Best regards

    Sven Zhao

  • 0 in reply to Sven Zhao
    TI__Mastermind 33275 points

    Again, we usually set the VSYSMIN lower than the VBAT, the system voltage should be stable all the time if minimum system capacitance is met, no additional circuitry is needed. 

  • 0 in reply to Tiger Zhou
    Prodigy 30 points

    Thanks Tiger,

    Actually, we have done a lot of test in past few days, we set the VSYSMIN lower than 4S VBAT to 13.8V，then once starting the charging, the system voltage will be in line with actual VBAT which will slowly grow up to max_charge_voltage 16.8V (as our target charging voltage).  And if we remove the battery after fully charged, the system voltage will be back to VSYSMIN.

    We tested the voltage with the BQ25720 evaluation board，but your answer have resolved our original problem. Thanks again.

    Best regards

    Sven Zhao